20. Movement sequencing abnormalities in schizophrenia: Changes in cortical activity during finger-tapping task

Abstract

Minor motor and sensory impairments, including movement sequencing, are frequent symptoms in schizophrenia. In a previous study ( Kasparek et al., 2012 ) we showed abnormal cortico-cerebellar functional connectivity during execution of motor task only in schizophrenia patients (SZP) with sequencing deficit. This suggests that the abnormal connectivity reflects rather symptoms that are domain-specific, than the diagnoses of schizophrenia per se. In order to parse out the differences in brain activity during motor learning that are disease-specific (i.e. common to all SZP relative to healthy controls) versus domain-specific (i.e. specific only to SZP with sequencing deficit), we conducted a new and more detailed analysis of the data from the previous study. We used functional magnetic resonance imaging to examine brain activity during finger-tapping task in 24 SZP and 24 healthy control participants. The task had two experimental conditions, in which participants had to execute blocks of sequenced finger movements (SQ condition) and non-sequenced movements (ALL condition). Prior to the imaging session, outside the scanner the movement sequencing skills were assessed through Neurological Evaluation Scale (NES). Based on the NES scores the patients were subdivided into two groups, those with sequencing abnormalities (SQ+), and those without movement sequencing deficit (SQ-). We performed whole brain analysis to identify regions with higher activation during SQ as compared to ALL blocks and we analyze these results as a function of movement sequencing skill. In the left motor and parietal cortices all patients had higher activation than healthy subjects in both ALL and SQ conditions. However, our analysis revealed that this effect was driven mainly by the SQ- subgroup in motor cortex, and by SQ + group in parietal cortex. No such differences were seen in the contra-lateral cortices. We conclude that executing a non-sequenced motor task is more demanding for SZP than controls (disease-specific), since they show constantly higher activation in left motor and parietal cortex. Notably, although the overactivation of motor cortex seems to be a good compensating strategy to achieve adequate motor performance, the hyperactivation of parietal cortex seems to be linked to motor deficit symptoms (domain-specific). Acknowledgement The study was supported by the Ministry of Health of the Czech Republic (research Grant No. NT13437) and by the University Hospital Brno from the Institutional Support Fund.